Centrifuge clinical chemistry analysis system

ABSTRACT

Medical testing apparatus including a centrifuge with a series of cuvettes received therein. The cuvettes may be discrete units or arranged in groups which make up cassettes. Each of the cuvettes has a test chamber or reaction chamber into which reagents and specimen pass during the centrifuging operation. The reagents are contained prior to centrifuging in plastic bags which include intentionally weak seams designed to fail during centrifuging and to permit the reagents to flow into the reaction chamber. The specimen is contained within a pipette tip closed by a cap. The cap is also designed to fail or, in other words, be centrifuged off of the pipette tip in order to permit the blood serum or plasma in the pipette tip to flow past the cap and into the reaction chamber after the red blood cells have been packed down into the cap by the centrifuging operation. After centrifuging, the cuvettes can be removed from the centrifuge and placed into a photometer to determine the amount of light passed or the amount of light passed can be determined directly while the cuvettes are being spun or turned in the centrifuge by a photometer.

United States Patent [191 Schmitz 1 Jan. 30, 1973 [75] Inventor: William David anapolis, 1nd.

Schmitz, Indi- [73] Assignee: Bio-Dynamics, Inc.,

' Ind.

[22] Filed: June 22, 1970 [21] App1.No.: 48,386

Primary Examiner-Morris O. Wolk Assistant Examiner-R. M. Reese Attorney-Woodard, Weikart, Emhardt & Naughton Indianapolis,

[57] ABSTRACT Medical testing apparatus including a centrifuge with a series of cuvettes received therein. The cuvettes may be discrete units or arranged in groups which make up cassettes. Each of the cuvettes has a test chamber or reaction chamber into which reagents and specimen pass during the centrifuging operation. The reagents are contained prior to centrifuging in plastic bags which include intentionally weak seams designed to fail during centrifuging and to permit the reagents to flow into the reaction chamber. The specimen is contained within a pipette tip closed by a cap. The cap is also designed to fail or, in other words, be centrifuged off of the pipette tip in order to permit the blood serum or plasma in the pipette tip to flow past the cap and into the reaction chamber after the red blood cells have been packed down into the cap by thecentrifuging operation. After centrifuging, the cuvettes can be removed from the centrifuge and placed into a photometer to determine the amount of light passed or the amount of light passed can be determined directly while the cuvettes are being spun or turned in the centrifuge by a photometer.

15 Claims, 16 Drawing Figures PATENTEDJAN 30 I975 SHEET 10F 4 INVENTOR. WILLIAM D. SCHM/TZ ATTORNEYS ing U. S. Pat. Nos.:

CENTRIFUGE CLINICAL CHEMISTRY ANALYSIS SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to testing apparatus and finds application in medical testing apparatus.

.2. Description of the Prior Art There is available in the prior art various devices and Certain devices and procedures marketed by applicants assignee pre-package some of the reagents for a given test in the test cuvette and precalibrate the meter used in the test. Other devices separate the test specimens by bubbles and move the test specimens along a tube whereby sequential testing is accomplished in a completely automatic fashion. These devices are subject to certain disadvantages. For example, there is presently no easy and convenient means and method for separating serum or plasma from the blood for use in the test procedure. The present standard procedure is to preprocess the blood in a conventional centrifuge. Also the above mentioned bubble separation test procedure is a very expensive device which is only appropriate in the larger laboratories and hospitals where substantial numbers of tests are carried out in a given period of time.

Certain other prior art is disclosed in the following articles: Analytical Techniques for Cell Fractions from Analytical Biochemistry 28, pp. 545-562 (1969); Computer lnterfaced Fast Analyzers From Science, Oct. 17, 1969, Volume 166, Number 3903; and Analytical Techniques for Cell Fractions" from Analytical Biochemistry 23, pp. 207-218 (1968) all of which relate to the simultaneous use of a centrifuge and a photometer. Other prior art is disclosed in the follow- 2,663,46l Brown Dec. 22, 1953 2,861,572 Hind et al. Nov. 25, 1958 2,984,146 Kwart et al. May 16,1961 3,026,764 Allen et al. March 27, 1962 3,050,239 Williams, Jr. Aug. 21, 1962 3,344,702 Wood et al. Oct. 3, 1967 3,415,627 Rait Dec. 10,1968 3,452,924 Schultz July 1, 1969 3,477,822 Hamilton Nov. 11,1969 3,481,712 Bernstein et al. Dec. 2, 1969 3,497,320 Blackburn et al. Feb. 24, 1970 SUMMARY OF THE INVENTION One embodiment of this invention might include medical test apparatus comprising a housing having a test chamber within which a test reaction is carried out, means for centrifuging said housing, a reagent container received within said housing and carried by said housing in spaced relation to said test chamber, said reagent container having a closure of predetermined strength sufficiently weak to fail and open under the action of said centrifuging means to permit flow of reagent from said container into said test chamber. The embodiment may also include a pipette tip and a cap on said pipette tip. The centrifuging means is operated to cause the red blood cells to be spun down into the cap. The speed of the centrifuge is then increased causing procedures for facilitating the running of medical tests. l

the cap to fly off the pipette tip and the serum in the tip to pass into the test chamber.

This invention also relates to a complete system for simultaneously and automatically processing a plurality of photometric chemical tests. Each unit test cell or cuvette is self contained with pre-packaged reagents. The general object of this invention is to overcome a major deficiency in the prior art by providing a means of processing whole blood directly, as an integral part of the test cycle. An advantage is that this invention-also provides a means of adapting most of the presently developed photometric clinical chemistry procedures which are designed for use with preprocessed serum or blood plasma, to whole blood procedures by a mechanical technique. This greatly reduces time required for testing, allows the use of extremely small amounts of blood (in the 25 micro-liter range) and significantly reduces the level of operator skill required. A second area of major improvement over the prior art is the pre-packaging of all reagents in separate cells of the reaction cuvette assembly. All of the critical dispensing of reagents is carried out in the production facility eliminating the need for the complex reagent dispensing and handling system presently built into automatic clinical analyzer systems in common use today. Because of this the cost and maintenance requirements of the instruments can be reduced and the ability to maintain accuracy improved.

Objects of the invention are to provide an improved test system and apparatus; to provide medical test apparatus which does not require a highly trained operator; to provide medical test apparatus capable of preprocessing whole blood directly as an integral part of the test procedure; to provide medical test apparatus which simplifies maintenance in the field because no bulk reagents are dispensed; and to provide medical test apparatus making possible use of a form of doublebeam spectrophotometry technique to cut down error because of change in light source intensity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cassette carrier;

FIG. 2 is a perspective view of a pipette and a sample tube;

FIG. 3 is a perspective view of the pipette and a cassette;

FIG. 4 is a perspective view of a centrifuge;

FIG. 5 is a longitudinal sectional view of an assembly including a curvette, a chassis, a pipette tip, a reagent containing bag, and a cap;

FIG. 5A is a perspective fragmentary view of the structure of FIG. 5 but showing the cap thereof in a different operating position;

FIG. 6 is a fragmentary perspective view of the cuvette, the cassette carrier, and a photocell arrangement;

FIG. 7 is an enlarged (as compared to FIG. 5) elevation of the chassis;

FIG. 8 is an end elevation of the structure illustrated in FIG. 7;

FIG. 9 is a section taken along the line 9-9 of FIG.

side

. FIG. 10 is an enlarged top plan view of the cuvette;

FIG. 13 is, an enlarged side elevation of the pipette P;

FIG. 14 is an enlarged plan view of the reagent containing bag; and

FIG. 15 is a side elevation of the structure illustrated in FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a sample tube 30 containing whole blood is illustrated and carries information on the label 31 concerning the contents and may be sealed or closed by a cap (not shown). In FIG. 3, a cassette 35 is illustrated which includes four cuvettes 36 connected together by plastic material 37. The top openings 38 in the cuvettes are sealed by a tear strip seal (not shown). Alsothe cassette is provided with a data card 33 carry ing information concerning the contents of the cassette. The plastic material 37 is bendable in the manner illustrated in FIG. 1 to permit the cassette 35 with its cuvettes 36 to be mounted or received within a cassette carrier 40 illustrated in FIG. 1. The cassette carrier 40 is shown in FIG. 1 with its top removed and as including a container 41 having a flat base 42 and upturned cylindrical side-walls 45. Mounted on the base 42 are retainer clips 46 which function to yieldably receive and resiliently hold in position'the cuvettes 36 of the cassette 35. As illustrated, the flat bottom 42 of the carrier includes a central circular opening 47 with a keyway 50 therein which permits locking of the eassette carrier in place in a centrifuge for rotation of the carrier and centrifuging of the contents thereof.

In FIG. 2, there is shown a pipette 51 which includes a pipette pump 52 and a pipette tip or container 55. The pipette is disclosed in the co-pending application for U. S. Letters Pat, Ser. No. 864,280, of I-Iinchman, Sommerville and Schmitz, assigned to the same assignee as the present invention. It is sufficient for present purposes to state that the pipette pump 52 functions to always draw in and dispense an equal volume of blood or other substance by suitable operation of the plunger 54. FIG. 13 shows in detail the construction of the pipette tip 55 as including a hollow interior 56 which has a tapered portion 57 facilitating attachment of the pipette tip 55 to the pipette pump. As shown in FIG. 3, the pipette pump 52 has an O-ring 60 mounted thereon which assists in effectively connecting the pipette tip 55 to the pump 52 in a leak proof manner. The O-ring seats in the cylindrical portion 58. The hollow interior 56 of the tip includes tapering portion 56' which tapers gradually from its larger end adjacent the cylindrical portion 58 down to the other smaller end 59 of the pipette tip 55. There is formed at that other end 59 reduced cylindrical portion 63 having a shoulder 61 for reception of a cap 62 shown in FIGS. and 5A. In use the pipette 51 is inserted into the cap 62 for attaching the cap to the reduced diameter cylindrical portion 63 and abutting the shoulder 61 of the pipette tip. The cap 62 is cylindrical and has a closed end 64' in addition to the open end 64.

Referring now to FIGS. 10, 11 and 12, a cuvette 36 is illustrated in more detail as including a generally cylindrical portion 100 and a flat portion 101. The cylindrical portion 100 has a generally cylindrical hollow interior 102 into which the chassis 105 of FIGS. 7, 8 and 9 is projected in operation of the present apparatus as described in more detail below. The flattened portion 101 of the cuvette has formed therein a test or reaction chamber and a reference chamber 106 which are separated by a partition 107.

Referring to FIGS. 7, 8 and 9, the chassis has a hollowed-out interior 110 formed with a shoulder or tapered portion 111 which functions to prevent further movement rightwardly as viewed in FIGS. 7 and 9 of the cap 62. The cap 62 is so sized as to be easily slidable in the hollow interior 110 without being loosely received whereby the cap will always have its closed end 64' projected toward the flattened end of the cuvette as shown in FIGS. 5A and 5. The hollow interior 110 is also formed with inwardly opening grooves 112 which permit blood (serum) or plasma to run past the cap rightwardly out of the open end 115 of the hollow interior 110. The chassis 105 also includes outwardly projecting ribs 116 which function to engage and hold the flexible plastic container of FIG. 23 between the chassis and the cuvette. It will be noted that the grooves l12 lead into grooves 114 which open into the tapered portion 111.

Referring now to FIGS. 2 through 6, the test procedure of the present invention is illustrated as including the placing of the pipette tip 55 in the blood contained within the container 30 for the obtaining of a sample of blood. This blood sample is precisely measured by operation of the pipette 51. The pipette is so operated as to withdraw the blood contained within the pipette tip slightly away from the tip and then the end of the pipette tip is wiped off. The end of the pipette is then inserted in a cap 62 in such a manner that the shoulder 61 abuts the cap. The pipette tip 55 with its cap 62 thereon is then inserted into the cuvette 36 of the cassette in the manner shown in FIGS. 3 and 5A.

As suggested by the drawings, quite a number of blood samples canbe carried by the cassette carrier at one time. The purpose of the cassette is to segregate four samples of blood of one person so that four different tests can be run on that blood at one time. Of course, various other persons cassettes can also be tested as suggested by the additional retainer clips 46 of the cassette carrier as shown in FIG. 1. The manner in which the pipette tip 55 with its cap thereon seats within the cuvette is illustrated in the cut-away FIG. 5A view. As illustrated the cap is press fitted on the reduced cylindrical projection 63 and abuts the shoulder 61. The cap is spaced from tapered portion 1 11. FIGS. 5 and 5A show in addition a reference component bag or container 200 and a reagent bag or container 201. As shown in FIG. 23 the reagent bags 201 and the reference component bag 200 are joined together as a part of the four bag group 202. These four bags are folded or cupped around the exterior of the chassis 105 so that the dividing areas 205 between the bags of the group contact the projections 116 illustrated in FIGS. 7, 8 and 9.

These projections 1 16 hold the container 202 against the inside wall of the cuvette 100. The group 202 of bags is so constructed that one edge 206, 207, 208 and 209 of the group of bags 202 is weaker than all the other edges thereof so that under centrifugal action the edges 206, 207, 208 and 209 fail, permitting dispensing of the contents of the bag by centrifugal force into the reaction chamber and the reference chamber. The bags 201 and 200 are so located that all of the bags 201 empty into the reaction chamber and only the bags 200 empty into the reference chamber. The weakness of the edges 206, 207, 208 and 209 is also designed so as to fail at a certain speed of the centrifuge, in other words, upon a certain number of gs being exerted on an edge. If desired, the edges can be designed to fail at different weaknesses. In this manner, the various reagents or contents of the bags can be discharged in order so as to cause the test reaction to be in accordance with predetermined standard test procedures.

Returning to the description of test procedure, the cassette with its four cuvettes and four pipette tips is then loaded into the centrifuge 300 as shown in FIG. 4 after the top 301 has been placed on the cassette carrier 40. The cassette carrier has apertures 302 in its base 42 as well as apertures 305 in its top. The apertures 302 and 305 are each aligned with a respective one of the flattened portions 101 of the cuvettes. The centrifuge 300 is capable of various speeds of rotation up to 10,000 rpm as desired by the operator. In one embodiment of the invention as shown in FIG. 6 a lamp 306, photocell 307 and light shield 310 with slit 311 are built into and are a part of the centrifuge. Another embodiment of the invention might include a standard colorimeter separate from the centrifuge and usable only after the centrifuging operation has been carried out. In such an embodiment the centrifuge would not incorporate a colorimeter or photocell.

It should be understood that, if the photometer is a part of the centrifuge and if readings are taken while the centrifuge is rotating, suitable electronic circuitry must be incorporated for separating the signals received from the various cuvettes. In such operation the reference chamber 106 provides the advantage of double beam spectrophotometry by making possible with a single beam a comparison of the absorbancy of a reference solution and-a sample. This comparison is made over a time interval which is short relative to the rate of change in intensity oflight source thus providing the advantage of double beam spectrophotometry.

In the test procedure the operator controls or may control the time at which various events occur. Thus, the first step in the process is the spinning down of the blood which may occur for example at l,800 rpm because of the small quantity of blood being spun down. Next the operator speeds up the centrifuge to the speed at which the cap 62 comes off of the centrifuge tip for example at 3,000 rpm. Further speeding up of the centrifuge to 8,000 rpm causes the first of the bags 200 and 201 to fail and all bags 200 and 201 have failed at 10,000 rpm. Various other bag failure speeds can be selected in order to accomplish the test procedure and timing desired. Alternatively, the centrifuge might be programmed to automatically reach the various speeds desired at various times desired so as to make the procedure entirely automatic.

FIG. 5 shows the cuvette just after the speed has been reached at which the cap is forced off of the pipette tip. Also shown is the discharging of the reagent bags into the reaction chamber 105 and the reference chamber 106. As illustrated, the cap 62 moves leftwardly against the tapered surface 11]. Prior to the leftward (as illustrated) movement of the cap in the hollow interior of the chassis, the red blood cells 400 in the blood have substantially all moved into the cap 62 so that serum fills the rest of the cap and also extends into the pipette tip. When the cap comes off the pipette tip and moves the relatively short distance from the tip to the tapered surface 111, the hollow interior 110 (which is basically cylindrical where the cap is) guides the cap preventing any of its contents from spilling. The substantial g forces acting on the cap and its contents level off the top (or rightward as illustrated) surface of the liquid in the cap so that the total contents of the cap are precisely determined. Also the cap moves only a very short distance so that splashing does not occur.

The cap might have a capacity of, for example, 0.0125 ml while the change of blood in the pipette tip and cap is, for example, 0.025 ml. During spinning down of the blood the red blood cells occupy perhaps 0.0833 of volume at the bottom (or leftward end as illustrated) of the cap. Thus, serum occupies the remainder of the contents of the cap as well as extends up into the pipette tip. Therefore, the liquid which flows into the reaction chamber is serum from the tip. This serum moves out of the pipette tip and through the grooves 112 and 114 and through the open end 115 when the cap comes away from the tip. The serum that flows in this manner intothe reaction chamber is a precise .0125 ml of liquid because of the centrifugal force action.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art. For example, the photometer optics might be built into the centrifuge in such a manner that, after the reactions are completed, the centrifuge head is stopped and then rotated by hand so as to successively position each cuvette into the light beam for a reading. Also the blood specimen might be diluted prior to placing the specimen in the pipette tip so as to make possible use of existing test procedures instead of requiring the setting up of new test procedures. In other words, the quantities are scaled down in order to keep the balance and therefore the same chemistries can be used.

Other applications of the invention might include analytical tests for water and air pollution, water treatment tests, as well as industrial chemical testing.

The invention claimed is:

1. Test apparatus comprising a pipette tip, a cap on said pipette tip, means for housing said pipette tip and cap, means for centrifuging said pipette tip and cap and housing means at a first speed until blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and for thenincreasing the speed of said centrifuging to a second speed sufficiently fast to cause said cap to fly off of said tip and at least a portion of said serum or plasma fraction to move past said cap, said cap gripping said pipette tip with sufficient force to remain thereon at said first speed but with insufficient force to remain thereon at said second speed.

2. Test apparatus comprising a housing having a test chamber within which a test reaction is carried out, means for centrifuging said housing, a reagent container received within and carried by said housing, said reagent container having a closure of pretermined strength sufficiently weak to fail and open under the action of said centrifuging means to permit flow of reagent from said reagent container into said test chamber.

3. Test apparatus as defined in claim 2 additionally comprising a chassis projecting into said housing and holding said reagent container against said housing, a pipette tip mounted-on said chassis and extending into said chassis, a cap on said pipette tip, said chassis having a hollow interior therein whithin which said cap is received and is movable from an on the tip position to an off the tip position, said means for centrifuging being operable at a first speed at which blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and at a second speed at which said cap comes off said tip and moves in said chassis to said off-the-tip position, said chassis having an open end into which said hollow interior opens and which leads into said test chamber, said chassis having grooves opening into said hollow interior and permitting flow of serum or plasma past said cap through said open end into said test chamber.

4. The test apparatus of claim 3 wherein said housing is a cuvette having a reference chamber alongside said test chamber, photocell means and light source means, said means for centrifuging being operable to rotate said cuvette repeatedly between said photocell means and said light source means in such a manner that said reference chamber and said test chamber are exposed in order.

5. The test apparatus of claim 4 wherein said reagent container is a flexible bag having a plurality of compartments therein, said bag having some of said compartments positioned to discharge into said test chamber and another of said compartments positioned to discharge into said reference chamber.

6. Test apparatus comprising a housing having a test chamber adapted to receive a specimen and reagents, said housing being adapted to be received in a centrifuge for centrifuge action thereon, a chassis member received in said housing, a pipette tip received in said chassis member, a cap on said pipette tip, reagent bags held between said housing and chassis, said cap being sufficiently securely attached to said tip to hold onto said tip while a blood specimen in said cap and tip is spun down into red blood cells and serum or plasma, said cap being sufficiently loosely attached to allow said cap to come off said tip'under increased centrifuge action, said chassis member having a hollow interior therein within which said cap is movable from an on the tip position to an off the tip position, said chassis member having grooves opening into said hollow interior permitting flow of serum or plasma past said cap into said test chamber.

7. Test apparatus comprising a cuvette having a test chamber withinwhich a test reaction is carried out, said cuvette also having a reference chamber positioned alongside said test chamber, means for centrifuging said cuvette, photocell means and light source means, said centrifuging means being arranged to rotate said cuvette repeatedly between said photocell means and said light source means in such a manner that said reference chamber and said test chamber are exposed in order.

8. Test apparatus comprising a pipette tip, a cap on said pipette tip, means for housing said pipette tip and cap, means for centrifuging said pipette tip and cap and housing means until blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and for then increasing the speed of said centrifuging sufficiently to cause said cap to fly off of said tip and at least a portion of said serum or plasma fraction to move past said cap, said housing means including a chassis, said pipette tip being mounted on said chassis so as to extend into said chassis with said cap on the portion of said tip which projects into said chassis, said chassis having a hollow interior therein within which said cap is received and is movable from an on the tip position to an off the tip position, said chassis interior being formed with a shoulder which provides the limit of movement of said cap when said cap moves into said off the tip position, said shoulder being closely spaced to said tip to prevent splashing of blood during said cap movement, said chassis havinggrooves opening into said hollow interior and permitting flow of serum or plasma past said cap.

9. Test apparatus comprising a container, a cap on said container, means for housing said container and cap, means for centrifuging said container and cap and housing means at a first speed until a specimen contained in said container and cap is spun down into a first fraction and a second fraction and for then increasing the speed of said centrifuging to a second speed sufficiently fast to cause said cap to fly off said container and at least a portion of said second fraction to move past said cap, said cap gripping said container with sufficient force to remain thereon at said first speed but with insufficient force to remain thereon at said second speed.

10. Test apparatus comprising a housing having a test chamber adapted to receive a specimen and reagents, said housing being adapted to be received in. a centrifuge for centrifuge action thereon, a chassis member received in said housing, a container in said chassis member, a cap on said container, reagent bags held between said housing and chassis, said cap being sufficiently securely attached to said container to hold onto said container while a specimen in said container and cap is centrifuged at a first speed and spun down into a first fraction and a second fraction, said cap being sufficiently loosely attached to allow said cap to come off said container under increased centrifuge action, said chassis member having a hollow interior therein within which said cap is movable from an on the container position to an off the container position, said chassis member having grooves opening into said hollow interior permitting flow of a portion of said specimen past said cap into said test chamber.

11. The test apparatus of claim 10 wherein said reagent bags have a closure of predetermined strength sufficiently strong to remain closed at said first speed but sufficiently weak to fail and open under said increased centrifuge action to permit flow of reagent from said reagent bags into said test chamber.

12. Test apparatus for spinning down blood into a first red cell fraction and a second serum or plasma fraction and for moving at least a portion of said second fraction away from said first fraction which comprises a container, a cap on said container, a housing for said container and cap, said container being mounted on of and away from said container when said means for centrifuging increases speed to said second speed.

14. The test apparatus of claim 13 wherein said housing has a test chamber, said test apparatus further including means for retaining said cap and container between said axis and said test chamber when said means for centrifuging centrifuges said housing and container.

15. Test apparatus comprising a housing having a test chamber adapted to receive a specimen and reagents, said housing being adapted to be received in a centrifuge for centrifuge action thereon, a chassis member received in said housing, a container in said chassis member, a cap on said container, said cap being sufficiently securely attached to said container to hold onto said container while a specimen in said container and cap is spun down into a first portion and a second fraction, said cap being sufficiently loosely attached to allow said cap to come off said container under increased centrifuge action, said chassis member having a hollow interior therein within which said cap is movable from an on-the-container position to an off-thecontainer position, said chassis member having a passage opening into said hollow interior permitting flow of a portion of said specimen past said cap into said test chamber.

UNITED STATES PATENT QFMQE CE'HHCATE M (IDREQTWN Patent No. 3 J13 77 D d J uary 30 1.973

Inventor(s) win-lam o 365111111312 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby eoneeteck as shown below:

Col. 4, line 54 Please delete Fig, 23 and insert -=--Fig,., M

Col. 5, line 64 Please delete "1&5" and insert 105' Signed and sealed this 20th day of November 1973..

(SEAL) Attest:

EDWARD M.F115]TCHER,JR I RENE D. 'IEG'I'D EEYER Attesting Officer Acting Commissioner of Patents 

1. Test apparatus comprising a pipette tip, a cap on said pipette tip, means for housing said pipette tip and cap, means for centrifuging said pipette tip and cap and housing means at a first speed until blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and for then increasing the speed of said centrifuging to a second speed sufficiently fast to cause said cap to fly off of said tip and at least a portion of said serum or plasma fraction to move past said cap, said cap gripping said pipette tip with sufficient force to remain thereon at said first speed but with insufficient force to remain thereon at said second speed.
 2. Test apparatus comprising a housing having a test chamber within which a test reaction is carried out, means for centrifuging said housing, a reagent container received within and carried by said housing, said reagent container having a closure of pretermined strength sufficiently weak to fail and open under the action of said centrifuging means to permit flow of reagent from said reagent container into said test chamber.
 3. Test apparatus as defined in claim 2 additionally comprising a chassis projecting into said housing and holding said reagent container against said housing, a pipette tip mounted on said chassis and extending into said chassis, a cap on said pipette tip, said chassis having a hollow interior therein whithin which said cap is received and is movable from an on the tip position to an off the tip position, said means for centrifuging being operable at a first speed at which blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and at a second speed at which said cap comes off said tip and moves in said chassis to said off-the-tip position, said chassis having an open end into which said hollow interior opens and which leads into said test chamber, said chassis having grooves opening into said hollow interior and permitting flow of serum or plasma past said cap through said open end into said test chamber.
 4. The test apparatus of claim 3 wherein said housing is a cuvette having a reference chamber alongside said test chamber, photocell means and light source means, said means for centrifuging being operable to rotate said cuvette repeatedly between said photocell means and said light source means in such a manner that said reference chamber and said test chamber are exposed in order.
 5. The test apparatus of claim 4 wherein said reagent container is a flexible bag having a plurality of compartments therein, said bag having some of said compartments positioned to discharge into said test chamber and another of said compartments positioned to discharge into said reference chamber.
 6. Test apparatus comprising a housing having a test chamber adapted to receive a specimen and reagents, said housing being adapted to be received in a centrifuge for centrifuge action thereon, a chassis member received in said housing, a pipette tip received in said chassis member, a cap on said pipette tip, reagent bags held between said housing and chassis, said cap being sufficiently securely attached to said tip to hold onto said tip while a blood specimen in said cap and tip is spun down into red blood cells and serum or plasma, said cap being sufficiently loosely attached to allow said cap to come off said tip under increased centrifuge action, said chassis member having a hollow interior therein within which said cap is movable from an on the tip position to an off the tip position, said chassis member having grooves opening into said hollow interior permitting flow of serum or plasma past said cap into said test chamber.
 7. Test apparatus comprising a cuvette having a test chamber within which a test reaction is carried out, said cuvette also having a reference chamber positioned alongside said test chamber, means for centrifuging said cuvette, photocell means and light source means, said centrifuging means being arranged to rotate said cuvette repeatedly between said photocell means and said light source means in such a manner that said reference chamber and said test chamber are exposed in order.
 8. Test apparatus comprising a pipette tip, a cap on said pipette tip, means for housing said pipette tip and cap, means for centrifuging said pipette tip and cap and housing means until blood contained in said tip and cap is spun down into its red cell fraction and its serum or plasma fraction and for then increasing the speed of said centrifuging sufficiently to cause said cap to fly off of said tip and at least a portion of said serum or plasma fraction to move past said cap, said housing means including a chassis, said pipette tip being mounted on said chassis so as to extend into said chassis with said cap on the portion of said tip which projects into said chassis, said chassis having a hollow interior therein within which said cap is received and is movable from an on the tip position to an off the tip position, said chassis interior being formed with a shoulder which provides the limit of movement of said cap when said cap moves into said off the tip position, said shoulder being closely spaced to said tip to prevent splashing of blood during said cap movement, said chassis having grooves opening into said hollow interior and permitting flow of serum or plasma past said cap.
 9. Test apparatus comprising a container, a cap on said container, means for housing said container and cap, means for centrifuging said container and cap and housing means at a first speed until a specimen contained in said container and cap is spun down into a first fraction and a second fraction and for then increasing the speed of said centrifuging to a second speed sufficiently fast to cause said cap to fly off said container and at least a portion of said second fraction to move past said cap, said cap gripping said container with sufficient force to remain thereon at said first speed but with insufficient force to remain thereon at said second speed.
 10. Test apparatus comprising a housing having a test chamber adapted to receive a specimen and reagents, said housing being adapted to be received in a centrifuge for centrifuge action thereon, a chassis member received in said housing, a container in said chassis member, a cap on said container, reagent bags held between said housing and chassis, said cap being sufficiently securely attached to said container to hold onto said container while a specimen in said container and cap is centrifuged at a first speed and spun down into a first fraction and a second fraction, said cap being sufficiently loosely attached to allow said cap to come off said container under increased centrifuge action, said chassis member having a hollOw interior therein within which said cap is movable from an on the container position to an off the container position, said chassis member having grooves opening into said hollow interior permitting flow of a portion of said specimen past said cap into said test chamber.
 11. The test apparatus of claim 10 wherein said reagent bags have a closure of predetermined strength sufficiently strong to remain closed at said first speed but sufficiently weak to fail and open under said increased centrifuge action to permit flow of reagent from said reagent bags into said test chamber.
 12. Test apparatus for spinning down blood into a first red cell fraction and a second serum or plasma fraction and for moving at least a portion of said second fraction away from said first fraction which comprises a container, a cap on said container, a housing for said container and cap, said container being mounted on said housing, means for centrifuging said housing and container at a first speed and for then increasing the speed of said centrifuging to a second speed, said cap gripping said container with sufficient force to remain thereon at said first speed but with insufficient force to remain thereon at said second speed.
 13. The test apparatus of claim 12 wherein said means for centrifuging rotates said housing about an axis with said container located between said axis and said cap whereby said cap moves radially outwardly off of and away from said container when said means for centrifuging increases speed to said second speed.
 14. The test apparatus of claim 13 wherein said housing has a test chamber, said test apparatus further including means for retaining said cap and container between said axis and said test chamber when said means for centrifuging centrifuges said housing and container. 